While it is said that an electroconductive (electrically conductive) polymer are generally excellent in stability against repetitive oxidation/reduction (doping/dedoping), an electroconductive polymer actually developed to a practical level is only polyaniline, but other electroconductive polymers known as wide as polyaniline, such as polypyrrole and polythiophene, have not been put to practical use as an active electrical element, primarily due to problems about durability.
As for possible applications of an electroconductive polymer material to active elements, there have been generally known applications to a hole injection layer in an organic light-emitting element (Patent Publication 1), to an overcurrent protective element (Patent Publications 2 and 3) and to a light-emitting element (Patent Publications 4 and 5), all of which are intended to apply an electroconductive polymer to electrical or electronic elements by itself. There has also been known a mixed film of an electroconductive polymer and a metal oxide, which is prepared by suspending fine particles of TiO2 or SiO2 in a pyrrole solution as electrolyte to allow a dopant to be doped homogeneously with mobility, and copolymerizing pyrrole to incorporate the fine particles having a particle diameter of 10 to 1000 nm into the obtained polymerized film (Patent Publication 6).
Patent Publication 1: Japanese Patent Laid-Open Publication No. 05-114487
Patent Publication 2: Japanese Patent Laid-Open Publication No. 09-246010
Patent Publication 3: Japanese Patent Laid-Open Publication No. 2002-134303
Patent Publication 4: Japanese Patent Laid-Open Publication No. 10-204426
Patent Publication 5: Japanese Patent Laid-Open Publication No. 2000-026851
Patent Publication 6: Japanese Patent Publication No. 06-074345